Rendering the route line requires layer specification

Nobody has claimed this yet.

Opening this issue as there are a few places where it does not work by default, and it seems there are many approaches to get the same answer. Each of which needs to specify relative layers.

``` kotlin
private val maneuverArrowBinder: ManeuverArrowBinder by lazy {
val routeArrowOptions = RouteArrowOptions.Builder(this.requireContext())
.withAboveLayerId("road-exit-shield")
.build()
val routeArrowView = MapboxRouteArrowView(routeArrowOptions)
val routeArrowApi = MapboxRouteArrowApi()
ManeuverArrowBinder(
this,
routeArrowApi,
routeArrowView,
routesViewModel
)
}
```

``` kotlin
private val options: MapboxRouteLineOptions by lazy {
MapboxRouteLineOptions.Builder(activity)
.withRouteLineResources(routeLineResources)
.withRouteLineBelowLayerId("road-label")
.build()
}
```

``` kotlin
private val routeArrowOptions by lazy {
RouteArrowOptions.Builder(mainCarContext.carContext)
.withAboveLayerId(PRIMARY_ROUTE_TRAFFIC_LAYER_ID)
.build()
}
```

cc: @cafesilencio

Start by tracing the RouteArrowOptions and MapboxRouteLineOptions entry points shown in the issue, including withAboveLayerId and withRouteLineBelowLayerId. Compare the route arrow and route line rendering paths to determine which relative-layer defaults are missing; done means the affected rendering cases work without requiring callers to specify those layers.

Written by the indexing model from the issue text.